Chapter 19

Question 1

Fill in the code in Comparable______ c = new Date();

Answer 1

C.Date

Question 2

Suppose List list = new ArrayList. Which of the following operations are correct?

		A.
list.add("Red");
		B.
list.add(new Integer(100));
		C.
list.add(new java.util.Date());
		D.
list.add(new ArrayList());

Answer 2

A.

list.add(“Red”);

Question 3

To declare a class named A with two generic types, use

Answer 3

B.
public class A -E, F- (Brackets, no parenthesis)

Question 4

To declare an interface named A with a generic type, use
		A.
public interface A { ... }
		B.
public interface A { ... }
		C.
public interface A(E) { ... }
		D.
public interface A(E, F) { ... }

Answer 4

A.

public interface A -E- (Brackets, no parenthesis)

Question 5

To declare an interface named A with two generic types, use
		A.
public interface A { ... }
		B.
public interface A { ... }
		C.
public interface A(E) { ... }
		D.
public interface A(E, F) { ... }

Answer 5

B.

public interface A -E, F- (Brackets, no parenthesis)

Question 6

To create a list to store integers, use

		A.
ArrayList list = new ArrayList<>();
		B.
ArrayList list = new ArrayList<>();
		C.
ArrayList list = new ArrayList();
		D.
ArrayList list = new ArrayList<>();

Answer 6

B.Integer (in brackets)

Question 7

To create a generic type bounded by Number, use

Answer 7

A.E extends number

Question 8

Which of the following declarations use raw type?

Answer 8

D.
ArrayList list = new ArrayList();

Question 9

If you use the javac command to compile a program that contains raw type, what would the compiler do?

		A.
report syntax error
		B.
report warning and generate a class file
		C.
report warning without generating a class file
		D.
no error and generate a class file
		E.
report warning and generate a class file if no other errors in the program.

Answer 9

E.
report warning and generate a class file if no other errors in the program.

Question 10

If you use the javac ?Xlint:unchecked command to compile a program that contains raw type, what would the compiler do?

		A.
report compile error
		B.
report warning and generate a class file
		C.
report warning without generating a class file
		D.
no error and generate a class file

Answer 10

B.
report warning and generate a class file

Question 11

Is ArrayList a subclass of ArrayList?
		A.
Yes
		B.
No

Answer 11

B. No

Question 12

Is ArrayList a subclass of ArrayList>?
		A.
Yes
		B.
No

Answer 12

A. Yes

Question 13

Is ArrayList a subclass of ArrayList extends Number>?
		A.
Yes
		B.
No

Answer 13

A. Yes

Question 14

Is ArrayList a subclass of ArrayList extends Number>?
		A.
Yes
		B.
No

Answer 14

A. Yes

Question 15

Is ArrayList> same as ArrayList extends Object>?

	A. Yes
	B. No

Answer 15

A. Yes

Question 16

Does super Number> represent a superclass of Number?

	A. Yes
	B. No

Answer 16

A. Yes

Question 17

Which of the following can be used to replace YYYYYYYY in the following code?

publicclassWildCardDemo3{
publicstaticvoidmain(String[] args) {
GenericStack stack1 =newGenericStack<>();
GenericStack stack2 =newGenericStack<>();
stack2.push("Java");
stack2.push(2);
stack1.push("Sun");
add(stack1, stack2);
WildCardDemo2.print(stack2);
}

	publicstaticvoidadd(GenericStack stack1,
	GenericStack stack2) {
	while(!stack1.isEmpty())
	stack2.push(stack1.pop());
	}
	}
		A.
? super Object
		B.
? super T
		C.
? extends T
		D.
? extends Object

Answer 17

B.

? super T

Question 18

ArrayList and ArrayList are two types. Does the JVM load two classes ArrayList and ArrayList?

A.
Yes
B.
No

Answer 18

B. No

Question 19

If E is a generic type for a class, can E be referenced from a static method?

	A. Yes
	B. No

Answer 19

B. No

Question 20

Fill in the most appropriate code in the blanks in the MyInt class?

publicclassMyIntimplements_______{
intid;

publicMyInt(intid) {
this.id = id;
}

publicString toString() {
returnString.valueOf(id);
}

	publicintcompareTo(\_\_\_\_\_\_\_ arg0) {
	if(id > arg0.id)
	return1;
	elseif(id < arg0.id)
	return-1;
	else
	return0;
	}
	}
		A.
Comparable / Object
		B.
Comparable / MyInt
		C.
Comparable / Object
		D.
Comparable / MyInt

Answer 20

B.

Comparable / MyInt

Question 21

To declare a class named A with a generic type, use

Answer 21

public class A -E- (in brackets)